Sharrow shared lane marking

A sharrow in Denver.

In a new study, two Colorado researchers found that sharrows (shared lane markings used on roads that are too narrow for bike lanes) do not make biking safer, and do not encourage more people to bicycle, Angie Schmitt reported for Streetsblog USA. The researchers from the University of Colorado Denver, Nick Ferenchak and Wesley Marshall, conducted their research in Chicago, before that city had many protected bike lanes. The men recently presented their study, “Relative (In)Effectiveness of Bicycle Sharrows on Ridership and Safety Outcomes,” in the Bicycling Research Mega Session of the 95th annual meeting of the Transportation Research Board.

Measuring Bicycle Commuting

Using Census block groups, Ferenchak and Marshall separated Chicago into three geographic sections, including: areas where bike lanes were added between 2008 and 2010, areas where sharrows were added, and areas with no bicycle treatments added. In examining the ways in which bike commuting and bicycling injuries changed over time, the two men found that bike commuting rates doubled in areas with new bike lanes, whereas there was a 43% increase in areas with no added sections, and only a 26% increase in places where shadows were added.

The researchers found that there was a greater decrease in injuries per bike commuter — 42% — where bike lanes were striped, as compared with only a 20% decrease in areas with sharrows. In areas with no added bicycle sections, there was a 36% decrease.

One problem with the study is that measuring bicycle commuters who live in a particular area is not the same as measuring the number of people who actually travel on those streets on bicycles. Still, the results strongly suggest that sharrows are ineffective as a safety strategy.

No Added Protection

Ferenchak told Streetsblog that sharrows seemed to have a small effect on encouraging people to bike but provide no additional protection. This is in line with what Dutch bike planner Dick Van Veen told the Hans on the Bike blog about sharrows in the Netherlands: They should be used in tandem with significant traffic-calming measures. On a street with fast traffic, to put down sharrows alone would be considered “unethical.”

The word “sharrows,” a mashup of the words “share” and “arrow,” was coined by Oliver Gajda, of the City and County of San Francisco Bicycle Program, according to the Wikipedia page “Shared Lane Marking.” The words “share” and “arrow” refer to San Francisco’s 2004 experiments with shared lane markings, in which that city developed a symbol consisting of a bicycle and two chevrons above it.

Sharrow Use in Denver

“Denver, Colorado, is widely acknowledged as the first domestic design and implementation of a shared lane marking, including a ‘bicycle stencil arrow’ in the 1993 Denver Bicycle Master Plan,” writes Darren Buck in an article titled “Overview and Applications of the ‘Sharrow” on BikePedantic.

In Denver, for example, there are 39 miles of sharrows, as opposed to 100 miles of bike lanes, according to In Denver, a designated bike lane is required to be at least 4 feet wide, but they are at least 5 feet wide in most locations, Denvergov writes. To make bicycling safer, Denver provides: designated bike lanes, buffered bike lanes (with increased separation between bicyclists and parked vehicles as well as vehicle traffic), protected bike lanes (dedicated, protected bike lanes at street level), and raised protected bike lanes (elevated above street level).

As this blog reported last September, Colorado Gov. John Hickenlooper announced a four-year, $100 million plan to boost bicycling in the state. The plan includes adding bicycle and pedestrian infrastructure, and funds for a better understanding and marketing of cycling, including projects to boost awareness and education to promote safety.

There has been a lively discussion among commenters to articles about Ferenchak and Marshall’s study. Here is just one of the comments, posted by Christopher Shimkin of Massachusetts, below a Treehugger article:

“We might further encourage bicycling regardless of paint or infrastructure if:

  1. more police officers patrolled using a bicycle,
  2. officers were strategically stationed during high traffic periods to enforce laws,
  3. more signage was included educate motorists, and
  4. vehicles parked in sharrow lanes are ticketed (w/o anyone having to alert the police).

Regarding No. 4, quite a few sharrows were included in my city over the past year but I’m incredulous about how often the lane (and sidewalk) is blocked by a parked vehicle.”

Image by Jeramey Jannene, used under its Creative Commons license.

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